Under ICAO Doc 4444, what criteria must be met before an aerodrome controller may issue a conditional line-up clearance (e.g., 'Behind landing Boeing 777, line up and wait Runway 12R behind')?

1. The aircraft or vehicle causing the condition must be seen by both the controller and the pilot, the condition must precede the instruction, and the word 'BEHIND' must be stated first and repeated at the end
2. The condition may be issued based solely on radar display position without visual contact by either party
3. The clearance may only be given at night when runway lights are set to maximum intensity
4. The controller must wait until the landing aircraft has completely vacated the runway before issuing the conditional instruction